1. Field of the Invention
The subject invention relates to a self-contained syringe with features for providing sterility, tamper evidence and needle shielding.
2. Background of the Invention
The prior art hypodermic syringe includes a generally cylindrical syringe barrel with opposed proximal and distal ends and a fluid receiving chamber therebetween. The proximal end of the syringe barrel defines a wide opening that receives a plunger in sliding, fluid-tight engagement with the walls of the syringe barrel. The distal end of the syringe barrel defines a narrow opening that permits a controlled fluid flow to or from the fluid receiving chamber in accordance with the direction of movement of the plunger. The distal end of the syringe barrel also is configured for receiving a needle cannula.
The prior art syringe must be packaged to ensure sterility until it is used. Some prior art syringes are sealed to protect their sterility in packages. These prior art syringes are accessed by opening the package shortly prior to use of the syringe. Other prior art syringes are considered self-contained in that the syringe barrel forms part of the sterile packaging. The typical prior art self-contained syringe includes a removable cap sealingly engaged over the proximal end of the syringe barrel to sterilely enclose both the wide entrance to the chamber and the plunger that is slidingly engaged in the chamber. The distal end of the prior art self-contained syringe also includes a removable cap-like shield that covers the needle cannula and sealingly engages the distal end of the syringe barrel. The caps of the prior art self-contained syringe are intended to define a barrier that bacteria cannot traverse. Thus the chamber, the plunger and the needle remain sterile until the syringe is used.
The prior art self-contained syringe is placed in condition for use by removing the proximal cap from the proximal end of the syringe barrel to expose the plunger and by removing the cap-like shield from the distal end of the syringe barrel to expose the needle cannula. The prior art self-contained syringe may then be filled with a selected dose of a drug, and the drug may be dispensed in a known manner. Self-contained hypodermic syringes of this type are commonly used by diabetic patients for self-administration of insulin.
Self-contained syringes offer many packaging conveniences and efficiencies with corresponding cost savings. However, prior art self-contained syringes do not provide the superior tamper evidence that is inherently provided by a separate hermetically sealed container for a syringe.
The cap-like needle shield of the above-described self-contained syringe often is discarded or misplaced immediately after the initial removal from the syringe barrel. Thus, if a sharps collector is not immediately available, the used hypodermic syringe may be left in an accessible location with the potentially contaminated needle fully exposed.
The prior art includes some hypodermic syringes with a syringe barrel and a tubular needle guard slidably mounted around the syringe barrel. The prior art tubular needle guard is releasably retained in a proximal position on the syringe barrel prior to use of the hypodermic syringe. In this pre-use condition, the needle cannula is protectively enclosed by a cap-like needle shield. Immediately prior to use, the cap-like needle shield is removed to expose needle cannula. The hypodermic syringe is then used with the tubular needle guard retained in its proximal position on the syringe barrel. After use of the hypodermic syringe, the tubular needle guard is slid distally along the syringe barrel and is locked into a position where the tubular needle guard protectively surrounds the used needle cannula. The prior art includes several different structures for releasably retaining the tubular needle guard in its proximal position and for locking the needle guard in its distal position. Hypodermic syringes of this general type are shown in U.S. Pat. Nos. 5,304,149; 5,342,309; 5,385,555; and 5,403,287.